JPH1089296A - Multistage compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the cooling gas wind amount required for cooling a motor without deteriorating economical efficiency in the no-load operation by connecting a joint passage at which branch passages extending from the downstream of an impeller on the rear stage side and an intermediate cooler are connected to each other, and forming a flowing passage in which cooling gas is allowed to flow to a high-speed motor. SOLUTION: An extracting part 14a is provided between an intermediate gas cooler 6a and a second stage compressor 1b, an extracting part 14b is provided on the way of a blow-off passage 18 downstream from a blow-off valve 9, and operating gas of a compressor 1 is extracted from them to cool a motor 2. The extracting parts 14a, 14b are positioned downstream from the gas coolers 6a, 6b, gas to be supplied from them is cooled to the ordinary temperature, and the motor 2 can be cooled by only gas flowing in the motor 2. Extracting passages 22a, 22b branched from the extracting parts 14a, 14b are joined into one passage downstream from check valves 22a, 22b and guided to the motor 2, the guided gas is discharged after cooling the motor 2, and it is guided to a rejoint part 15 between a suction throttle valve 7 and a first stage compressor 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multi-stage compressor,
In particular, it relates to a multi-stage compressor supported by magnetic bearings.

[0002]

2. Description of the Related Art Japanese Utility Model Laid-Open No. 3-19498 discloses that a compressed gas of a compressor is branched and extracted to cool a motor or a magnetic bearing, and the extracted gas is supplied as a cooling gas for the motor or the magnetic bearing. Have been. In this prior art, a centrifugal impeller is provided at the end of the rotating shaft of the electric motor,
The compressor is constituted by supporting the motor rotor with magnetic bearings, and the compressor constitutes a refrigeration cycle together with the condenser and the evaporator. Here, a part of the refrigerant in the refrigeration cycle is sprayed from the spray nozzle to cool the magnetic bearing and the coil of the electric motor.

[0003] Japanese Patent Application Laid-Open No. 64-79999 discloses a compressor in which a compression stage is connected to a high-frequency motor.
A configuration is shown in which the rotating shaft is supported by a magnetic bearing and is covered by a common housing that is confidential to the outside. In this compression device, a gas-side conduit provided between a plurality of compression stages acts as a surface cooler. That is, a part of the compressed gas re-cooled in the surface cooler is supplied to the rotor of the high-frequency motor, the rotor for excitation, and the magnetic bearing through the supply passage for cooling, and then the suction pipe is discharged through the discharge passage. It is returned to a piece.

[0004]

When the cooling device described in the above-mentioned prior art is disclosed in Japanese Utility Model Laid-Open No. 3-19498 is applied to a multi-stage compressor having a large compression ratio, the amount of the cooling device can be adjusted to the amount required during no-load operation. Therefore, the cooling gas must be extracted from the downstream of the final stage, and excessive cooling air flows during load operation, which is uneconomical. Conversely, if the cooling gas is extracted from the intermediate stage with an emphasis on economy, there is a problem in that the extraction unit has a negative pressure during the no-load operation, and the cooling gas cannot be ventilated into the electric motor. Further, the cooling device described in the above publication relates to a centrifugal compressor for driving a refrigeration cycle, and is premised on using a refrigerant or a cooling medium for cooling an electric motor or a magnetic bearing. In the case of a compressor that compresses, a sufficient cooling effect cannot be obtained.

[0005] Japanese Patent Application Laid-Open No. 64-8, which is the latter of the above prior art,
The compression device described in Japanese Patent Application No. 0799 has to have a split casing structure, and a coil-shaped surface cooler surrounds the casing, so that a large number of steps and labor are required for assembly. No consideration is given to cooling during no-load operation. Furthermore, it is not considered that the condensed liquid is discharged from the surface cooler, and condensate is accumulated in the surface cooler when used for compressing air or the like containing water vapor, or the condensed liquid splashes on the cooling gas. And condensed inside the compressor.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned disadvantages of the prior art, and to provide a multistage compressor having a simple structure, which does not impair the economy during load operation and which is necessary for cooling the motor even during no load operation. The purpose is to secure a cooling gas flow rate. ◆
Another object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to provide a multi-stage compressor having a simple configuration supported by magnetic bearings, without impairing the economics during load operation and without load operation. In some cases, the purpose is to secure a cooling gas flow rate necessary for cooling the magnetic bearing. Another object of the present invention is to realize a highly reliable multi-stage package type centrifugal compressor having a small size and a simple structure.

[0007]

According to a first aspect of the present invention, there is provided a first stage including a high-speed motor having a rotating shaft and impellers mounted on both ends of the rotating shaft. And a second stage compression stage, and an intercooler provided between the first stage and the second stage compression stage. A suction throttle valve is provided on the side, and a blow-off valve is provided on the discharge side, respectively, and branch paths branching from the downstream side of the downstream impeller and the downstream side of the intercooler are provided, and these branch paths are connected to each other. A junction is formed, and the junction and the high-speed motor are connected to form a flow passage through which the cooling gas flows.

According to a second aspect of the present invention, there is provided a high-speed electric motor having a rotating shaft and supporting the rotating shaft by a magnetic bearing, and an impeller mounted on both ends of the rotating shaft. Including a first stage and a second stage compression stage, and an intercooler provided between the first stage and the second stage compression stage,
In a multi-stage compressor capable of switching between load operation and no-load operation, a suction throttle valve is provided on the suction side of the compressor, a blow-off valve is provided on the discharge side, and the downstream side of the downstream impeller and the downstream of the intercooler. A branch path is provided from each side, and the branch paths are connected to each other to form a merging path, and the merging path is connected to a high-speed motor to form a flow path through which the cooling gas flows through the magnetic bearing. .

Preferably, a drain recovery section is provided in the intercooler, or a branch path provided downstream of the downstream impeller has a branch position downstream of the blow-off valve. A pressure reducing valve is provided in a branch pipe provided with a check valve and branched from a downstream side of the intercooler. More preferably, a control means for changing the opening of the pressure reducing valve between a load operation and a no-load operation is provided.

[0010] Preferably, a flow control means for controlling on / off of a flow in each branch building is provided. And more preferably, at the time of no-load operation, the flow in the branch pipe branched from the downstream side of the subsequent impeller is turned on, and the flow in the other branch pipe is turned off, or at the time of load operation, the intercooler is used. This turns on the flow in the branch pipe branched downstream of the pipe and turns off the flow in the other branch pipes.

A return passage for returning the cooling gas cooled by the high-speed motor to the upstream of the suction throttle valve may be formed, or a return passage for returning the cooling gas cooled to the magnetic bearing upstream of the suction throttle valve. May be formed.

According to a third aspect of the present invention, there is provided a high-speed motor having a rotating shaft, and first and second compression stages including impellers mounted on both ends of the rotating shaft. And an intercooler provided between the first and second compression stages, wherein the multi-stage compressor is capable of switching between a load operation and a no-load operation. A cooling passage for cooling and a cooling passage for cooling the high-speed motor during a no-load operation of the compressor are branched from different positions between the intercooler and the blow-off valve. In any of the above embodiments, the impeller is preferably a centrifugal impeller.

According to a fourth aspect of the present invention, there is provided a high-speed motor having a rotating shaft, and first and second compression stages including impellers mounted on both ends of the rotating shaft. And an intermediate cooler provided between the first and second compression stages, wherein the multistage compressor is capable of switching between a load operation and a no-load operation. First and second branch paths are provided downstream of the cooler, and pressure detection means for detecting discharge pressure is provided on the discharge side of the compressor. Load operation and no-load operation are performed based on the output of the pressure detection means. An operation control means for switching operation is provided, a connection path is formed by connecting the first and second branch paths, and a flow path for connecting the connection path and the high-speed motor to flow the cooling gas through the high-speed motor. Is formed.

According to a fifth aspect of the present invention, there is provided a first stage including a high-speed motor having a rotating shaft supported by a magnetic bearing, and impellers mounted on both ends of the rotating shaft. And the second stage compression stage and the first and second stage compression stages.
An intercooler provided between the first and second compression stages, wherein the multistage compressor is capable of switching between a load operation and a no-load operation. And the second branch, provided with pressure detection means for detecting the discharge pressure on the discharge side of the compressor, and provided with operation control means for switching between load operation and no-load operation based on the output of the pressure detection means, A junction is formed by connecting the first and second branch paths, and a flow path for flowing the cooling gas through the magnetic bearing is formed by connecting the junction and the high-speed motor.

That is, according to the multistage compressor of the present invention, since the cooling gas of the electric motor is supplied from the plurality of branch extraction units, the compressor is discharged from the middle stage of the compressor during the load operation and is discharged to the atmosphere during the no-load operation. Cooling gas can be supplied from the air passage for cooling the motor, and thereby, the amount of cooling gas required for cooling the motor can be secured even during no-load operation without impairing the economy during load operation.

Further, in the multi-stage compressor of the present invention, switching between the load operation and the no-load operation is made possible, and the cooling gas of the magnetic bearing is branched and extracted from a plurality of branches. From the stage, the cooling gas can be supplied from the air discharge passage during the no-load operation, thereby reducing the cooling gas flow rate required for cooling the magnetic bearing even during the no-load operation without impairing the economy during the load operation. Can secure

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a three side view showing a schematic external shape of the multistage compressor according to the present invention. The suction filter 13 and the suction throttle valve 7 linked to the blow-off valve 9 are arranged at the upper part of the compressor, and the gas coolers 6a and 6b are arranged at the lower part of the compressor. 1st stage compressor 1a
And the 2nd stage compressor 1b has a suction nozzle in the outer peripheral portion,
The suction gas 4a, 4b flows in from the radial direction. Further, the discharge nozzle of the first stage compressor and the suction nozzle and the discharge nozzle of the second stage compressor are directly connected to the gas cooler to realize a compact structure.

The extraction section 14a is provided on the outer peripheral portion of the casing of the second stage compressor, and a relatively low-temperature gas cooled by the gas cooler 6a from a suction section immediately before the impeller of the second stage compressor. Has been extracted. Immediately after the branch portion 14a, an orifice 31 is provided as a pressure reducing means.
On the other hand, the extraction part 14b is located in front of the suction filter 13 and communicates with the air discharge passage 18 upstream of the suction throttle valve 7 and downstream of the air discharge valve 9 inside the filter.

Check valves 20a and 20b are installed in the flow paths branched from the extraction sections 14a and 14b, respectively.
The cooling gas branch box 32 is connected downstream of the check valves 20a and 20b. Although not explicitly shown in the drawing, cooling gas supply units 29a, 29b, 29 provided on the outer peripheral surface of the electric motor are provided.
The flexible tubes are connected between c and 29d and the cooling gas branch box. Similarly, the cooling gas discharge unit 30
The cooling gas discharged from a, 30b, 30c, 30d, and 30e is guided to the cooling gas junction box 33 by a flexible tube. The gas after cooling the electric motor 2 assembled in the cooling gas merging box 33 passes through the re-merging portion 15 provided on the outer peripheral portion of the casing of the first stage compressor, and then the first gas is cooled.
It is returned to the suction section immediately before the impeller of the stage compressor.

Here, the electric motor 2 is an inverter-controlled high-speed electric motor, and the rotating shaft is supported by magnetic bearings. Although not shown, a power supply panel, an inverter panel, a magnetic bearing control panel, and the like are required for driving the compressor, and are installed adjacent to the compressor 1.

The flow and details of one embodiment of the multi-stage compressor shown in FIG. 2 will be described with reference to FIGS. FIG. 1 is a flowchart of a compressor system showing a configuration of a first embodiment of a multistage compressor according to the present invention. In this embodiment, a multi-stage compressor is used for generating a constant-pressure gas such as a factory air source, and air is used as a handling gas.

In FIG. 1, a compressor 1a constituting a low-pressure stage and a compressor 1b constituting a high-pressure stage of the multi-stage compressor 1 include:
Each has at least one centrifugal impeller. These impellers are attached to both ends of a rotating shaft 3 extending from the main body of the electric motor 2, and are driven to rotate with the rotation of the electric motor 2. The electric motor 2 is a high-speed electric motor in which the rotating shaft 3 is supported by a magnetic bearing, and generates heat due to iron loss of a coil provided in the drive unit and the magnetic bearing unit and wind loss due to high-speed rotation.

A suction throttle valve 7 and a filter 13 are provided upstream of the first stage compressor 1a. After the suction gas 4 of the compressor is removed by the filter 13, the suction throttle valve 7 is removed.
And is guided to the first stage compressor 1a. Further, an intermediate gas cooler 6a is provided between the first stage compressor 1a and the second stage compressor 1b, and the gas whose pressure has been raised by the first stage compressor 1a and whose temperature has risen is cooled by a gas cooler. After being cooled in 6a, it is guided to the second stage compressor 1b. The filter 13
Upstream is open to the atmosphere. Further, the suction gas is generally humid air containing water vapor.

When the gas sucked into the compressor is pressurized, the partial pressure of water vapor increases. When the pressurized gas is cooled by the gas cooler 6a, the saturation pressure of water vapor decreases, and the relative humidity of the gas increases. Depending on the conditions of the sucked atmosphere, after the relative humidity of the gas becomes 1 at a temperature during the cooling, if the gas is further cooled, a part of the steam condenses to generate fog or dew. In the first embodiment of the present invention, the condensate generated in this manner accumulates in the gas cooler, and the gas cooler has a structure capable of continuously discharging the drain out of the gas cooler. I have. As a result, the relative humidity becomes 1 or less on the downstream side of the gas cooler whose absolute humidity is smaller than that on the upstream side, and there is no possibility of condensation of water vapor. In this embodiment, a device for separating the condensed liquid from the gas is not particularly installed in order to simplify the structure, but an eliminator or a demister may be provided on the downstream side of the gas cooler. Separation can be performed more reliably.

Downstream of the second-stage compressor 1b, a gas cooler 6b, a check valve 10, and a receiver tank 12 are provided, and a discharge gas 5b of the second-stage compressor 1b is supplied to the gas cooler 6b.
After being cooled in b, a part thereof is stored in the receiver tank 12, and the rest is supplied to each gas consumer downstream. A blow-off passage 18 branches from between the gas cooler 6 b and the check valve 10, and a blow-off valve 9 is provided in the middle of the blow-off passage 18. By opening the blow-off valve 9, the second stage compressor 1b
Can be guided to the suction filter 13. According to the present embodiment, since the air discharge passage 18 is guided to the suction filter 13 and the filter also functions as a silencer, the structure is simplified. Needless to say, a separate silencer may be provided and opened to the atmosphere.

Since the pressure downstream of the check valve 10 is the supply pressure to the process, the multi-stage compressor 1 is controlled so as to keep this pressure substantially constant. Therefore, a pressure measuring device 11a for measuring the supply gas pressure is provided downstream of the check valve.
A control device 11 is provided for controlling the constant wind pressure based on the gas pressure measured by the pressure measuring device 11a. The control signals 19a and 19b from the control device 11 are
To the suction throttle valve 7 and the compressor 1
Control the operating state of the

The operating state of the compressor 1 is controlled in accordance with the pressure of the gas supplied to the process. When the pressure of the supplied gas is lower than a predetermined pressure set in advance in the controller 11, the suction throttle is set. The normal operation is performed by opening the valve 7 and closing the blow-off valve 9. On the other hand, when the amount of gas consumed in the process is small and the supply gas pressure exceeds the set pressure, the blow-off valve 9 is opened to prevent surging of the compressor 1 and save power consumption. At the same time, the suction throttle valve 7 is controlled to a throttle-free operation state (actually, the load decreases but does not become zero).

During load operation, the suction throttle valve 7 is open, so that the pressure of the suction gas 4a of the first stage compressor 1a is substantially equal to the atmospheric pressure and about 1 atm. The first stage compressor 1a and the second stage compressor 1b are both designed to have a compression ratio of about 3 at the specification point, and the discharge gas 5a of the first stage compressor 1a and the second stage compressor 1b The pressure of the suction gas 4b is about 3 atm, and the pressure of the discharge gas 5b of the second stage compressor 1b is about 9 atm.

During the no-load operation, the blow-off valve 9 is opened and the suction throttle valve 7 is throttled to keep the compression ratio at about 3, so that the pressure on the upstream side of the blow-off valve 9 (discharge of the second stage compressor 1b) (Approximately equal to pressure) is about 1.5 due to the pressure loss of valves and lines.
Atmospheric pressure, the suction gas pressure of the second stage compressor 1b and the discharge gas pressure of the first stage compressor 1a are about 0.5 atm, and the suction gas pressure of the first stage compressor 1a is about 0.2 atm.

An extraction unit 14a is provided between the intermediate gas cooler 6a and the second stage compressor 1b, and an extraction unit 14b is provided in the middle of the air discharge passage 18 downstream of the air discharge valve 9, respectively. The working gas of the compressor 1 is extracted from these extraction units for cooling the electric motor 2. The extraction units 14a and 14b are located downstream of the gas coolers 6a and 6b, respectively, and the gas supplied from them is cooled to about room temperature, so that the electric motor 2 can be cooled only by ventilating the electric motor 2. . The pressure reducing valve 8 and the check valve 20a are provided in the extraction flow path 22a branched from the extraction part 14a, and the check valve 20b is provided in the extraction flow path 22b branched from the extraction part 14b. These extraction flow paths 22a, 22b are provided with check valves 20a,
Downstream of 20b, they are combined into one and guided to the electric motor 2. The gas guided to the electric motor 2 is exhausted after cooling the electric motor 2, and is introduced to a rejoining portion 15 between the suction throttle valve 7 and the first-stage compressor 1 a. In addition, although the extraction flow paths 22a and 22b are combined into one downstream of the check valves 20a and 20b, they may be directly led to the electric motor 2 without being combined.

At the time of load operation, the gas pressures of the extraction section 14a and the re-merging section 15 are about 3 atmospheres and about 1 atmosphere, respectively, as described above.
Atmospheric pressure. Since the blow-off valve 9 is closed, there is no gas flow in the blow-off passage 18, and the gas pressure of the extraction unit 14b is equal to the pressure of the suction filter 13 and about 1 atm. Therefore, the pressure of the extraction unit 1 is
While there is a pressure difference of about 2 atm in 4a, the pressure difference in the extraction section 14b becomes almost zero, so the cooling gas 16 is supplied exclusively from the extraction section 14a. Since the differential pressure at which the gas air flow required for cooling the electric motor 2 can be secured is approximately 0.5 to 1 atm, a sufficient amount of cooling gas can be supplied to the electric motor 2 from the extraction unit 14a located between the stages.

In order to extract the cooling gas not from the downstream of the final stage but from the intermediate stage, it is sufficient to secure a minimum necessary air volume as the cooling gas, and it is possible to obtain a larger air volume through the work of the compressor. High-energy gas is wasted. Further, in consideration of economy, since the differential pressure of about 2 atm is still too large for cooling the motor, it is better to restrict the pressure reducing valve 8 and reduce the pressure to the minimum necessary pressure before introducing the pressure to the motor 2.

At the time of no-load operation, the suction throttle valve 7 is throttled, so that the gas pressures of the extraction section 14a and the re-merging section 15 are about 0.5 atm and about 0.2 atm, respectively, as described above. Then, the blow-off valve 9 is opened to flow the gas also into the blow-off passage 18, and the flow passage is throttled by a throttle 21 such as an orifice or a throttle valve provided between the extraction part 14 b and the suction filter 13 in the middle of the blow-off passage. As a result, a gas pressure of slightly more than one atmosphere is obtained in the extraction unit 14b. However, even if the aperture 21 is not provided, the extraction unit 14
Since the pressure of b is about 1 atm, which is almost equal to that of the suction filter section, the pressure difference with respect to the pressure of the re-merging section 15 is
At about 0.3 atm, and at the extraction unit 14b at about 0.8 atm,
The cooling gas 16 is exclusively supplied from the extraction unit 14b. As a result, the amount of cooling gas required for cooling the electric motor can be secured even during the no-load operation.

At the time of no-load operation, since the wind speed and the iron loss of the magnetic bearing do not change and the iron loss of the motor drive unit is reduced because the rotation speed is constant, the required cooling air flow is smaller than at the time of the load operation. A throttle such as an orifice or a throttle valve may be provided in the middle of the extraction flow path 22b branched from the extraction unit 14b to further reduce the amount of air flow to the electric motor. However, with this configuration, there is little economic merit during no-load operation aside from load operation. Further, the cooling gas may be introduced directly from the atmosphere, not from the middle of the ventilation passage 18. In this case, since the water vapor in the atmosphere may be condensed in the electric motor, a dust filter is required at the suction port.

FIG. 3 schematically shows the internal structure of the motor 2 and the compressors 1a and 1b in the first embodiment shown in FIG. 1, and the supply path of the motor cooling gas.

In FIG. 3, the first stage compressor 1a and the second stage compressor 1a
The stage compressor 1b has centrifugal impellers 28a and 28b, respectively, and these centrifugal impellers are directly attached to both ends of the rotating shaft 3 protruding from the main body of the electric motor 2. Electric motor 2
Is a high-speed motor of an inverter control type, in which a drive unit 24 is disposed in the center, and a rotary shaft is provided with two sets of radial magnetic bearings disposed between the drive unit 24 and the two impellers 28a, 28b. 25a, 25b. Also, the drive unit 24 is moved from the radial bearing 25b on the second stage compressor 1b side.
On the side, axial magnetic bearings 26a and 26b that carry the axial thrust generated in the compressor 1 are provided.

In the motor 2 of this embodiment, iron loss, which is an electrical loss in a coil and the like, and wind loss caused by high-speed rotation of a rotating body are heat-generating factors. 24 and radial magnetic bearings 25a, 25b,
The axial magnetic bearings 26a and 26b and the gap between these and the rotating body. During the load operation of the compressor, the heat generated by the motor driving unit 24 is large, and the heat generated by the magnetic bearing is small. Further, when the compressor is operated under no load, the amount of heat generated by the windage does not change because the rotation speed is constant, but the driving power of the electric motor 2 is reduced. Become.

In order to cool the heat generated from these heat sources, a part of the gas which is pressurized by the compressor and cooled by the gas cooler is extracted and supplied to the electric motor 2 as the cooling gas 16. The electric motor has a total of four cooling gas supply units 29a, 29b, 29c, and 29d in the vicinity of each heat source, and each supply unit has supply ports at a plurality of circumferential positions. I have. Also, the exhaust after cooling the motor 2 is:
Again, a total of five discharge units 30a, 30b, 30c, 30
It is discharged from a plurality of discharge ports in the circumferential direction provided in d and 30e.

Radial magnetic bearing 2 on the first stage compressor 1a side
The cooling gas 16a for mainly cooling the 5a is guided from the cooling gas supply unit 29a to a space formed between the radial magnetic bearing 25a and the impeller 28a. A part of the cooling gas is discharged from the discharge part 30a together with the leakage flow from the first stage compressor 1a, and the rest cools the magnetic bearing 25a through the gap between the radial magnetic bearing 25a and the rotating shaft 3,
It is discharged from the discharge unit 30b. Similarly, the cooling gas 16b
Is discharged from the discharge portions 30b and 30c after cooling the driving portion 24 of the electric motor, the cooling gas 16c is discharged from the discharge portion 30d after cooling the axial magnetic bearing 26a, and the cooling gas 16d is discharged from the axial magnetic bearing 26b. After cooling the radial magnetic bearing 25b, the discharge portions 30d and 3
0e.

The passage of the cooling gas 16 inside the electric motor 2 is complicated and diverse, and the pressure loss from the supply section to the exhaust section differs for each supply section position. Therefore, in order to secure a ventilation amount necessary for cooling each heat generating unit, each supply unit 29 is required.
a, 29b, 29c, and 29d, upstream of the throttles 27a, 27b, and 17 for adjusting the air volume such as orifices and valves, respectively.
c and 17d are provided.

In this embodiment, the impeller of the compressor is directly mounted on the rotating shaft of the electric motor. However, the impeller may be connected by a coupling or the like, and the number and arrangement of the impellers are not limited to this. . That is, the present invention can be commonly applied to a multi-stage compressor capable of switching between load operation and no-load operation. As described above, by adopting the configuration shown in FIGS. 1 to 3, the amount of cooling gas required for cooling the electric motor or the magnetic bearing can be ensured even during no-load operation without impairing the economy during load operation. A multi-stage compressor can be realized.

FIG. 4 shows a schematic configuration of a second embodiment of the multi-stage compressor according to the present invention. This second embodiment differs from the first embodiment shown in FIG. 1 in the cooling gas flow path from the extraction units 14a and 14b to the electric motor 2. In addition, the same reference numerals indicate the same parts.

In FIG. 4, gas extracting portions 14a and 14b for cooling the electric motor 2 are provided between the intermediate gas cooler 6a and the second stage compressor 1b and the blow-off valve 9 as in the first embodiment. Is located in the air discharge passage 18 downstream of. Check valves 20a and 20b are respectively installed in the extraction flow paths 22a and 22b led from the extraction units 14a and 14b. In addition, these extraction flow paths 22a and 22b are connected to the check valve 2
Downstream of 0 a and 20 b, they are combined into one and passed through a pressure reducing valve 8 and then guided to the electric motor 2. The degree of opening of the pressure reducing valve 8 can be adjusted according to the operation state of the compressor in the load operation and the no-load operation, and the control signal 19 c is obtained from the control device 11.

Also in the second embodiment, the extraction unit 14
The pressures of a, 14b and the re-merging section 15 are the same as those in the first embodiment, and are about 3 atm, about 1 atm, about 1 atm during the load operation, and about 0.5 atm, respectively at the no-load operation. The pressure is about 0.2 atm. Therefore, similarly to the first embodiment, the cooling gas is supplied from the extracting unit 14a during the load operation and from the extracting unit 14b during the no-load operation.

In this embodiment, the extraction units 14a, 14a
Both of the cooling gas supplied from b pass through the pressure reducing valve 8. At the time of load operation, the extraction unit 1
Since the pressure at 4a is about 2 atm higher, if the pressure reducing valve is throttled, the gas flow required for cooling the electric motor 2 is ventilated. During a no-load operation, the pressure reducing valve 8 is opened to secure a ventilation amount necessary for cooling the electric motor 2. As described above, the opening degree of the pressure reducing valve 8 is controlled according to the operation state of the load operation or the no-load operation based on the control signal 19c from the control device 11, and at this time, the control device 11 controls the pressure reducing valve together with the constant wind pressure control signal. 8 is transmitted.

With the above configuration, the same effect as in the first embodiment can be obtained in the second embodiment.
That is, the amount of cooling gas required for cooling the electric motor or the magnetic bearing can be ensured even during the no-load operation without impairing the economy during the load operation.

FIG. 5 shows a schematic configuration of a third embodiment of the multistage compressor according to the present invention. This third embodiment differs from the first embodiment shown in FIG. 1 in the cooling gas flow path from the extraction units 14a and 14b to the electric motor 2. In addition, components denoted by the same reference numerals in the drawings indicate the same components.

In FIG. 5, the gas extracting portion 14a for cooling the electric motor 2 is located between the intermediate gas cooler 6a and the second stage compressor 1b, as in the first embodiment. on the other hand,
Unlike the first embodiment, the extraction unit 14 b is located in the air discharge passage 18 upstream of the air discharge valve 9. This extraction unit 14
b does not necessarily need to be in the air discharge passage 18 and may be downstream of the gas cooler 6b provided downstream of the second stage compressor 1b having substantially the same pressure. Since the extraction unit 14b is located upstream of the blow-off valve 9, a device corresponding to the throttle 21 in the first embodiment is unnecessary.

The supply passages branched from the extraction sections 14a and 14b are connected to a three-way valve 23, and the cooling gas is supplied to the electric motor 2 from only one of them. The path of the three-way valve is switched according to the operation state of the load operation and the no-load operation of the compressor, and a control signal 19 d for the switching is output from the control device 11. A pressure reducing valve 8 is provided between the extraction unit 14a and the three-way valve.

In the third embodiment, the pressures in the extraction section 14a and the re-merging section 15 are the same as in the first embodiment,
The pressure is about 3 atm and about 1 atm during the load operation, and about 0.5 and 0.2 atm respectively during the no-load operation.
The pressure of the extraction unit 14b is substantially equal to the discharge pressure of the second stage compressor 1b, and is about 9 atm during the load operation and about 1.5 atm during the no-load operation.

In the first and second embodiments, the path of the cooling gas of the electric motor 2 is passively determined by the pressure of the extraction units 14a and 14b, whereas in the third embodiment, the three-way valve 8 is switched. It is actively determined by Here, the three-way valve is switched by the control signal 19 from the control device 11.
Based on d, control is performed according to the operation state of the load operation and the no-load operation, and at this time, the control signal of the pressure reducing valve 8 is output from the control device 11 together with the constant wind pressure control signal.

During load operation, the three-way valve 23 is
It is opened to the side of the flow path branched from a. The cooling gas is reduced to a minimum necessary air volume in the pressure reducing valve 8 and supplied to the electric motor 2. The extraction unit 14b is located upstream of the blow-off valve 9 and its pressure is as high as about 9 atm. However, since the three-way valve 23 is closed for the flow path branched from the extraction unit 14b, it is uneconomical. There is no possibility that a large amount of gas is ventilated to the electric motor 2.

During no-load operation, the three-way valve 23 is connected to the extraction unit 1
It is open to the side of the flow path branched from 4b. At this time,
The differential pressure of the extraction unit 14b with respect to the pressure of the re-merging unit 15 is about 1.3 atm, and it is possible to sufficiently secure the flow rate of the cooling gas required for cooling the electric motor.

With the above-described configuration, the same effects as those of the first embodiment can also be obtained in the third embodiment, that is, without impairing the economy during load operation. Even during the no-load operation, the amount of cooling gas required for cooling the electric motor or the magnetic bearing can be secured.

In the above description, a two-stage centrifugal compressor has been described as an example. However, it goes without saying that a centrifugal compressor with three or more stages can be similarly operated. Further, the compressor is not limited to the centrifugal type, but may be an axial flow type or a positive displacement type.

[0056]

As is apparent from the above detailed description, according to the multistage compressor according to the present invention, since the cooling gas of the electric motor is extracted from the plurality of extraction units, the compressor is operated during the load operation. From the middle stage, the cooling gas can be extracted from the air discharge passage during the no-load operation, and the flow rate of the cooling gas required for cooling the magnetic bearing can be ensured even during the no-load operation without impairing the economy during the load operation.

Further, in the multi-stage compressor supported by the magnetic bearing according to the present invention, the cooling gas of the magnetic bearing is configured to be extracted from the plurality of extraction portions. The cooling gas can be extracted from the air discharge passage during the load operation, and the amount of cooling gas required for cooling the magnetic bearing can be secured even during the no-load operation without impairing the economy during the load operation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of a multistage compressor according to the present invention.

FIG. 2 is a top view, a front view, and a side view of the first embodiment of the multi-stage compressor according to the present invention.

FIG. 3 is a longitudinal sectional view of the first embodiment of the multi-stage compressor according to the present invention, showing details inside the compressor.

FIG. 4 is a configuration diagram of a second embodiment of the multi-stage compressor according to the present invention.

FIG. 5 is a configuration diagram of a third embodiment of the multi-stage compressor according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor, 1a ... First stage compressor, 1b ... Second stage compressor, 2 ... Drive motor, 3 ... Rotary shaft, 4 ... Suction gas, 4a
1st stage compressor suction gas, 4b 2nd stage compressor suction gas, 5 discharge gas or supply gas, 5a 1st stage compressor discharge gas, 5b 2nd stage compressor discharge gas, 6 gas Cooler, 6a: Intermediate gas cooler, 6b: Discharge gas cooler, 7
... Suction throttle valve, 8 ... Pressure reducing valve, 9 ... Outlet valve, 10 ... Check valve, 11 ... Pressure detector and control device, 12 ... Receiver tank, 13 ... Suction filter, 14 ... Extraction unit, 14a ... Load operation Extraction unit at the time, 14b ... extraction unit at the time of no-load operation, 1
5: Rejoining part, 16a, 16b, 16c, 16d: Motor cooling gas, magnetic bearing cooling gas, 17a, 17b, 17
c, 17d, 17e: Exhaust gas after cooling, 18: Blow-off passage, 19a: Blow-off valve drive signal, 19b: Suction throttle valve drive signal, 19c: Reducer valve drive signal, 19d: Three-way valve drive signal, 20a ... Check valve, 20b check valve, 21 throttle, 2
2: Extracted gas, 22a: Extracted gas during load operation, 22b
... Extracted gas during no-load operation, 23 ... Three-way valve, 24 ... Drive section of electric motor, 25a, 25b ... Radial magnetic bearing, 26
a, 26b: axial magnetic bearings, 27a, 27b, 2
7c, 27d: throttle valve, 28: impeller, 28a: first stage compressor impeller, 28b: second stage compressor impeller, 29a,
29b, 29c, 29d: cooling gas supply unit, 30a, 3
0b, 30c, 30d, 30e: cooling gas discharge unit.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naohiko Takahashi 603, Kandachicho, Tsuchiura-shi, Ibaraki Pref.

Claims (17)

[Claims] 1. A high-speed electric motor having a rotating shaft, and first and second stages including an impeller mounted on both ends of the rotating shaft.
A multi-stage compressor comprising a stage compression stage and an intercooler provided between the first stage and the second stage compression stage and capable of switching between a load operation and a no-load operation. The throttle valve is provided with a blow-off valve on the discharge side, and branch paths are provided from the downstream side of the impeller and the downstream side of the intercooler on the downstream side, respectively. A multi-stage compressor, wherein a passage is formed, and the high-speed electric motor is connected to the merged flow passage to form a flow passage through which the cooling gas flows through the high-speed electric motor. 2. A high-speed electric motor having a rotating shaft and supporting the rotating shaft by a magnetic bearing, a first stage and a second stage compression stage including impellers mounted on both ends of the rotating shaft; An interstage cooler provided between the first and second compression stages, wherein a multistage compressor capable of switching between a load operation and a no-load operation is provided. A suction throttle valve is provided on a suction side of the compressor, and a suction throttle valve is provided on a discharge side. A blow-off valve is provided, and a branch path branched from the downstream side of the impeller and the downstream side of the intercooler on the subsequent stage is provided, and the branch paths are connected to form a merging flow path. A multi-stage compressor, wherein the high-speed motor is connected to form a flow passage through which the cooling gas flows through the magnetic bearing. 3. The multi-stage compressor according to claim 1, wherein a drain recovery section is provided in the intercooler. 4. A first and second stage including a high-speed motor having a rotating shaft, and impellers mounted on both ends of the rotating shaft.
A multistage compressor comprising a stage compression stage and an intercooler provided between the first stage and the second stage compression stage, wherein the load operation can be switched between a load operation and a no-load operation. A cooling passage for cooling the high-speed motor and a cooling passage for cooling the high-speed motor during a no-load operation of the compressor are branched from different positions between the intercooler and the blow-off valve. And a multi-stage compressor. 5. The multi-stage compressor according to claim 1, wherein a check valve is provided between the branch path and the junction path. 6. The multi-stage compressor according to claim 1, wherein the branch path provided downstream of the rear-stage impeller has a branch position downstream of the blow-off valve. . 7. The multi-stage compressor according to claim 1, wherein a pressure reducing valve is provided in a branch pipe branched from a downstream side of the intercooler. 8. The multi-stage compressor according to claim 7, further comprising control means for changing the opening of said pressure reducing valve between a load operation and a no-load operation. 9. The multi-stage compressor according to claim 1, further comprising flow control means for controlling on / off of a flow in each of the branch buildings. 10. The multi-stage compressor according to claim 9, wherein, during a load operation, a flow in a branch pipe branched downstream of the intercooler is turned on, and a flow in another branch pipe is turned off. . 11. The multi-stage according to claim 10, wherein during a no-load operation, a flow in a branch pipe branched from a downstream side of a subsequent impeller is turned on, and a flow in another branch pipe is turned off. Compressor. 12. The multi-stage compressor according to claim 1, wherein a return flow path for returning the cooling gas that has cooled the high-speed motor to a position upstream of the suction throttle valve is formed. 13. The multi-stage compressor according to claim 2, wherein a return flow path is formed for returning the cooling gas that has cooled the magnetic bearing upstream of the suction throttle valve. 14. A high-speed motor having a rotating shaft, first and second compression stages including impellers mounted on both ends of the rotating shaft, and a first stage and a second stage between the first and second stages. A multi-stage compressor having an intercooler provided and capable of switching between a load operation and a no-load operation, wherein a cooling passage for cooling the high-speed motor during a load operation of the multi-stage compressor; A multi-stage compressor provided with a cooling passage for cooling the high-speed motor during operation, wherein at least one of the cooling passages is branched from a substantially atmospheric pressure atmosphere. 15. The multi-stage compressor according to claim 1, wherein said impeller is a centrifugal impeller. 16. A high-speed electric motor having a rotating shaft, first and second compression stages including impellers mounted on both ends of the rotating shaft, and between the first and second compression stages. An intercooler provided in the multistage compressor that can switch between a load operation and a no-load operation, wherein a first stage and a second stage are provided downstream of the impeller and downstream of the intercooler on the downstream side. A pressure detection means for detecting a discharge pressure on the discharge side of the compressor, and an operation control means for switching between a load operation and a no-load operation based on the output of the pressure detection means, A multi-stage compressor, wherein a junction is formed by connecting the first and second branch paths, and the junction is connected to the high-speed motor to form a flow passage through which the cooling gas flows in the high-speed motor. Machine. 17. A high-speed motor having a rotating shaft supported by a magnetic bearing, first and second compression stages including impellers mounted on both ends of the rotating shaft, and the first and second stages. An intercooler provided between the two compression stages,
In a multi-stage compressor capable of switching between a load operation and a no-load operation, first and second branch paths are provided downstream of the impeller and downstream of the intercooler on the downstream side, and the discharge side of the compressor is provided. Is provided with pressure detecting means for detecting the discharge pressure, and operation control means for switching between load operation and no-load operation based on the output of the pressure detecting means is provided, and connects between the first and second branch paths. A multi-stage compressor, wherein the merging channel is formed by connecting the merging channel and the high-speed motor to form a flow passage through which the cooling gas flows through the magnetic bearing.